The present invention deals with an improved construction of an internal valve quick release air cannon. Devices of this type are utilized to accumulate pressurized air and, upon receipt of a controlled signal, to rapidly discharge a burst of pressurized air into the interior of a storage hopper. The intermittent bursts of pressurized air promote the flowability of material in the hopper preventing hang up and bridging of material internal to the hopper. Typical prior art arrangements are shown in U.S. Pat. Nos. 3,942,684 and 4,051,982 issued to applicant. These patents illustrate "external valve" arrangements in which the piston and valve are located outside of the tank. One example of an "internal valve" arrangement is shown in U.S. Pat. No. 3,788,527 of applicant. This aerator, like the present arrangement, has the piston and valve assembly disposed inside the pressure tank.